Reader WebView enables allowFileAccessFromFileURLs in two font modes

[jim-daf]

The article WebView built in me.ash.reader.ui.component.webview.WebViewLayout.get() mutates two WebSettings flags inside the standardFontFamily when block:

ReadingFontsPreference.GoogleSans -> {
    allowFileAccess = true
    allowFileAccessFromFileURLs = true
    "sans-serif"
}
ReadingFontsPreference.External -> {
    allowFileAccess = true
    allowFileAccessFromFileURLs = true
    "sans-serif"
}

Two concerns with this:

1. allowFileAccessFromFileURLs = true lets scripts running on a file:// page issue XHR requests against other file:// resources. The reader WebView is fed with article HTML via loadDataWithBaseURL / loadUrl and is not normally a file:// document, so the flag has no positive effect on font rendering, but it broadens the blast radius for any future code path or third-party HTML that does end up on a file URL. On minSdk <= 29 (this project ships minSdk = 26) it stays in effect on real devices.

2. allowFileAccess = true is unnecessary for the GoogleSans branch. Google Sans is bundled in app assets and reached via file:///android_asset/, which is allowed even when setAllowFileAccess(false) is in force on every supported Android version. So the flag only matters for the External font preference, where the user explicitly picks a font file from device storage.

CWE-200 (Exposure of Sensitive Information) is the closest CWE mapping for the universal flag combination on a JavaScript-enabled WebView that also registers a JS bridge (JavaScriptInterface.NAME).

Suggested fix:

• Drop both allowFileAccess = true and allowFileAccessFromFileURLs = true from the GoogleSans branch.
• Drop allowFileAccessFromFileURLs = true from the External branch and keep allowFileAccess = true there, since that mode genuinely loads a user-chosen file.

A PR with that change is open at #1277 and does not affect the font behaviour for any of the existing reading-fonts options.